Different foods have different amounts of water in it, and even the same food could have varying moisture from batch to batch. However, the main elements that dictate the drying time is very dynamic and range from what you’re dehydrating, how much you’re dehydrating, to how humid the environment is. A tray of celery will take significantly longer to dry than a tray of apples because celery is 95% water while apples are 84%, there’s just more water to remove.

Moreover, you can fit more celery on a tray than apples. Which brings us to the second point: total load. The amount of airflow and temperature stays the same, but it now has to remove more water. Imagine you have a bucket with 2 gallons of water in it and there’s a small hole at the bottom draining the water. If you add 2 more gallons it will take longer to drain, unless you make the hole bigger so it can drain faster. Unfortunately for us, the hole in this analogy is the rate at which our dehydrator can remove moisture, which we can’t really change. The more food you have in the dehydrator, the more moisture needs to be removed and the longer it will take.

Lastly, humidity is also a consideration. Those who live in humid climates or experience exceptionally humid days will need more time to dry the same item than someone who lives in the high desert where humidity is low. However, all this is negated if you dehydrate in a room with functioning air conditioning as that conditions air to a consistently comfortable low humidity level.